JP2761700B2 - Manufacturing method of heavy concrete - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing heavy concrete having excellent radiation shielding properties and suitable for use in, for example, a concrete cask which is a container for storing spent fuel. The heavy concrete can be used in a building or the like in a nuclear power plant where dimensional restrictions are severe, and can also be used when a heavy material is required as a weight.

[0002]

2. Description of the Related Art A large amount of depleted uranium is produced as a by-product from a uranium enrichment process in accordance with a uranium enrichment business by nuclear fuel production. The DU primarily in the United States, the pigment in the initial catalyst is used in other chemical products, also have been military applications to ammunition, etc. In some, the demand is small, at most forms of UF ₆ It is currently stored as fuel for fast breeder reactors, which are expected to be put to practical use in the future. Also in Japan, in addition to storing highly concentrated waste by-produced by the establishment of a nuclear fuel cycle, due to the small size of the national land, in particular, the storage of the large amount of depleted uranium generated from the enrichment process also requires facilities. And costs are a problem.

On the other hand, spent fuel used in nuclear power generation is stored in a storage rack in a dedicated storage pool. When shielding radiation using concrete, there are two methods, a method of increasing the thickness to improve the shielding property, and a method of increasing the weight to achieve the same purpose. Usually,
Although the shielding performance is ensured by increasing the thickness, the use of heavy concrete (also referred to as heavy concrete) can reduce the wall thickness and floor thickness.

[0004] Although this heavy concrete has been used conventionally, iron ore mainly composed of magnetite has been added to increase the specific gravity. That is, in this heavy concrete, it is necessary to increase the iron ore, which is an aggregate, in order to increase the shielding ability. However, the amount of the iron ore is limited, and the construction is performed as the specific gravity of the concrete increases. Also become difficult. Generally, the specific gravity of ordinary concrete is about 2.1 g / cm ^3, weight concrete are conventionally used gravity is often that of 3 to 4 g / cm ^3.

[0005]

By the way, instead of storing the spent fuel by the storage pool and the dedicated rack,
In a concrete spent fuel storage container called a concrete cask, which is expected to be developed in the future, dimensional restrictions on wall thickness and floor thickness are strict, and heavy concrete with improved shielding capacity is required.

However, in the above-mentioned conventional heavy concrete, as described above, there is a problem such as workability in increasing the specific gravity to increase the shielding property, and in consideration of the workability, the concrete thickness is increased. This causes a problem that the number of stored fuels is limited. The reduction in the number of fuel containers directly leads to the deterioration of economic efficiency, and the improvement of the shielding property of the concrete is an important issue in the future.

The present invention has been made in view of the above situation. As described above, the present invention focuses on depleted uranium, which is currently mostly stored as waste, and uses it as aggregate or mixed material. It is an object of the present invention to obtain heavy concrete having higher shielding performance by using it for concrete.

[0008]

That is, the feature of the method for producing heavy concrete according to the present invention that meets the above-mentioned object is that concrete containing water and aggregate added to cement and mixed is used for converting depleted uranium as an oxide to the aggregate . And nuclear fuel
Mix with cement in the form of sintered pellets such as pellets
And the specific gravity is controlled to 3 to
It is in the process of producing concrete in the range of 6 g / cm ³ . In the method of the present invention, the depleted uranium is also possible separately Rukoto added another aggregate. In addition,
Here, the specific gravity is the specific gravity of the concrete after hardening.

[0009]

According to the production method of the present invention, heavy concrete containing depleted uranium is produced, and this heavy concrete is
When comparing the gamma ray dose rate with conventional iron ore-containing heavy concrete of the same specific gravity and conventional ordinary concrete under the same thickness (about 60 cm), the gamma ray dose rate is When used, it could be reduced to about 1/1000 of ordinary concrete, but in the case of the heavy concrete containing depleted uranium according to the present invention, the gamma dose rate was 1/4 or less of this conventional heavy concrete. And could be.

According to the heavy concrete of the present invention, if the specific gravity is, for example, 5 g / cm ³ , about 3 t of depleted uranium can be employed per 1 m ^{3 of} heavy concrete, so that a large amount of surplus is obtained. It is very useful as a method for utilizing this depleted uranium.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional view showing a concrete cask manufactured by the method for manufacturing heavy concrete of the present invention. In the figure, 1 is a container lid, 2 is an inner lining made of stainless steel, and 3 is heavy concrete containing depleted uranium. Is shown.

In the method for producing heavy concrete containing depleted uranium, when water is added to kneaded cement and mixed, degraded uranium having higher shielding performance than conventional iron ore is used as an aggregate to be mixed therein. As a form of depleted uranium to be mixed, a stable uranium oxide (UO ₂ or
Most preferably, U ₃ O ₈ ) is used, and this uranium oxide is mixed with the cement in the form of sintered pellets such as nuclear fuel pellets.

It is also preferable to prepare iron ore such as general aggregate and magnetite separately and mix them with cement.

On the other hand, in the production of the above heavy concrete, care must be taken since uranium itself contains radioactivity. Further, although the mixing ratio of each element material is different depending on the specific gravity of the heavy concrete to be finally achieved, since the specific gravity of each element material is considerably different, it is necessary to prepare a stirrer such as an omni mixer. Further, an admixture or the like is used as necessary.

On the other hand, depleted uranium oxide pellets (sintered
In the case of using the body , the pellet can be used as a part of the aggregate, and it is possible to aim at a heavy concrete having a higher specific gravity than in the case of using the powder. The precautions for handling during production are as described above .
In addition, since the thickness of concrete is usually 50 cm or more when used as heavy concrete, even if the above-mentioned uranium oxide is mixed with cement in the form of lumps such as pellets, the shielding capacity is partially increased.

Further, since the gamma ray shielding ability is higher as the specific gravity of concrete is higher and the atomic number of the substance to be mixed is higher, even if the specific gravity of heavy concrete is the same, the present invention contains depleted uranium. The heavy concrete has a higher gamma ray shielding ability than the conventional iron-containing heavy concrete.

[0017] As the specific gravity of the weight concrete, if too low shielding ability is lowered, because that could interfere with too high workability such as, is suitable in the range of ³ ~6g / cm 3.

Thus, according to the production method of the present invention, as an example, heavy concrete containing depleted uranium having a specific gravity of 4.5 g / cm ³ was produced, and this was replaced with a conventional iron ore having the same specific gravity of 4.5 g / cm ^3. The gamma ray dose rate was compared with the heavy concrete contained and conventional ordinary concrete (specific gravity 2.1 g / cm ³ ) under the same thickness conditions.

The dose rate of gamma rays can be reduced to about 1/10 that of ordinary concrete by using conventional heavy concrete.
00 or less, but in the case of the heavy concrete according to the present invention, furthermore,
The gamma dose rate was less than 1/4.

According to the heavy concrete of the present invention, if the specific gravity is, for example, 4.5 g / cm ³ , approximately 2.4 t of depleted uranium can be employed per 1 m ^{3 of} heavy concrete. It can be said that this method is extremely effective also as a method of utilizing the surplus depleted uranium.

[0021] Having described the embodiments of the present invention, aggregate or the like other than depleted uranium, also added pressure, also without the addition, the intended purpose of the present invention can be achieved It is.

[0022]

As described above, in the method for producing heavy concrete of the present invention, when water is added to cement and kneaded, degraded uranium is used as an aggregate to be mixed with the oxide.
And in the form of sintered pellets such as nuclear fuel pellets.
And a concrete having a specific gravity in the range of ³ to 6 g / cm ^3.
Are those formed with the cleat, instead of a conventional iron ore, and sintered pellets excellent depleted uranium shielding properties as oxide
By adopting it in the form of heavy concrete with high specific gravity
The gamma ray dose rate can be reduced by 1 / compared to conventional heavy concrete of the same specific gravity and thickness.
4 or less, thereby avoiding the severe dimensional restrictions of future concrete casks without difficulty. Remarkable effect of maintaining the shielding performance of this cask and building it to the specified design dimensions. Is played.

Further, according to the heavy concrete of the present invention, if the specific gravity is, for example, 5 g / cm ³ , about 3 t of depleted uranium is used per 1 m ^{3 of} heavy concrete, so that a large amount of depleted uranium is used. It can be said that the surplus depleted uranium is extremely effective in treating and using the same.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a concrete cask manufactured by the method for manufacturing heavy concrete of the present invention.

[Explanation of symbols]

 1 Container lid 2 Inner lining 3 Heavy concrete containing depleted uranium

Claims (2)

(57) [Claims] [Claim 1]. In concrete where water and aggregate are added to cement and mixed, depleted uranium is used as the aggregate.
Oxide and in the form of sintered pellets such as nuclear fuel pellets
Mixed with cement in state, the range specific gravity of 3 to 6 g / cm ³
A method for producing heavy concrete, characterized by producing concrete . 2. The method for producing heavy concrete according to claim 1, wherein another aggregate is added separately from the depleted uranium.